A well-known example of a cogeneration apparatus is disclosed in Japanese Patent Application Laid-Open Publication No. 2006-9678 (JP 2006-9678 A), in which an engine compartment is partitioned off within a housing (referred to as a “cogeneration case” below); an engine, an electrical generator, and a heat exchanger are provided to the engine compartment; and a ventilation fan and a radiator fan are provided for ventilating the engine compartment. Specifically, the interior of the cogeneration case is partitioned into the engine compartment, a duct compartment, a radiator compartment, and the like; and the engine, the electrical generator, and the heat exchanger are provided to the engine compartment. The ventilation fan is provided to a dividing wall between the engine compartment and the duct compartment, and the radiator fan is provided to the dividing wall between the radiator compartment and the exterior.
In the cogeneration apparatus disclosed in JP 2006-9678 A, the ventilation fan and the radiator fan are driven, whereby the ventilation fan allows air to be led to engine compartment from an exterior part, and allows air in the engine compartment to be led to the duct compartment. The radiator fan allows air in the duct compartment to be led to the radiator compartment, and allows air in the radiator compartment to be led to the exterior part. It is thereby possible for the air in the engine compartment to be ventilated, and the electrical generator and other components in the engine compartment to be cooled. In other words, the ventilation fan and the radiator fan serve as cooling fans.
However, the cogeneration apparatus according to JP 2006-9678 A is configured such that the engine and the electrical generator are provided to the engine compartment, and the air in the engine compartment is ventilated, whereby the electrical generator is cooled. The air in the engine compartment therefore rises due to the heat of the engine, and the risen air cools the electrical generator. Therefore, in order to cool the electrical generator, the size of the ventilation fan and the radiator fan must be increased, an air flow adequate for ventilation must be ensured, and rising of air in the engine compartment due to the heat of the engine must be limited.
Accordingly, the noise when driving the fans (i.e., the noise accompanying ventilation) increases when the ventilation fan and the radiator fan are increased in size. More heat than necessary is pulled from the engine and the heat exchanger, and making efficient use of the waste heat of the engine (motor) as a heat source is difficult.